单选题In a normally operating diesel engine, the main cause of lubricating oil contamination in the crankcase is a result of the （）.Ametal particles loosened by wearBair when no air cleaners are usedCcondensation of water vaporsDbreakdown of the lubricating oil by dilution
单选题
In a normally operating diesel engine, the main cause of lubricating oil contamination in the crankcase is a result of the （）.
A
metal particles loosened by wear
B
air when no air cleaners are used
C
condensation of water vapors
D
breakdown of the lubricating oil by dilution
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